Semiconductor processing involves a number of processing steps in which individual layers are masked and etched to form semiconductor components. Mask alignment is important as even small misalignments can cause device failure. For certain photomasking steps, proper alignment is extremely critical to achieve proper fabrication. In others, design rules are more relaxed allowing for a larger margin for alignment errors. One way in which design rules can be relaxed is to provide processing sequences which enable so-called self aligned etches, such as to encapsulated word lines in the fabrication of memory circuitry. Further, there is a goal to reduce or minimize the number of steps in a particular processing flow. Minimizing the processing steps reduces the risk of a processing error affecting the finished device, and reduces cost.
This invention arose out of needs associated with improving the manner in which semiconductor memory arrays, and in particular capacitor-over-bit line memory arrays, are fabricated.